Body controlled heat range and extended gap spark plug

ABSTRACT

A spark plug for internal combustion engines wherein heat range is controlled by body configuration and the dissipation of heat through an extended nose portion of the body that extends beyond the &#39;&#39;&#39;&#39;reach&#39;&#39;&#39;&#39; to protectively enclose an extended insulator and center electrode, and that is exposed within the combustion chamber with the spark gap positioned at the &#39;&#39;&#39;&#39;eye&#39;&#39;&#39;&#39; of combustion and/or at an optimum ignition point. The heat range of the spark plug is efficiently controlled by means of the exposure and the fineness ratio of the extended nose portion of the spark plug body and heat transferred therefrom through threaded engagement that is of assured tightness adjacent the combustion chamber.

Linsay Sates atent 1 1111 3,825,784 1451 July 23,1974

1 41 BODY CONTROLLED HEAT RANGE AND EXTENDED GAP SPARK PLUG [76]Inventor: Maurice E. Lindsay, 700 E. 11611 A St., No. 7, Los Angeles,Calif.

22 F1166; Sept. 25,1972 [21] Appl. No.: 291,975

, 1 123/169 C [51] Int. Cl. H0lt 13/16 [58] Fieid of Search... 313/143,118, 140, 138-138, 313/115, 144; 123/169 C, 169 R, 169 EL [56]References Cited UNITED STATES PATENTS 1,163,272 12/1915 Simmons313/l1.5 1,338,674 5/1920 Champion 313/143 1,443,215 3/1923 HaSbIOUCh123/169 EL 1,449,781 3/1923 Ring 313/138 1,717,034 6/1929 Hoffmanm,313/143 2,620,784 12/1952 Cipriani 313/143 FOREIGN PATENTS ORAPPLICATIONS; 166,549 7/1922 Great Britain 313/144 OTHER PUBLICATIONS1161111, P. M.,"The Gasoline Automobile Its Deseign' and ConstructionVol. 111 Electrical Equipment, ILIFFE & Sons Ltd., 1920, pp. '96,98-102, 104-105. Byc'hinsky, W. A.,Factors Affecting Functioning ofSpark Plugs, SAE Quart. Trans. 2, April 4, 1948, pp. 255-267.

Obert, E. F., Internal Combustion Engines, Analysis & Practice,lnternation Textbook Co., 2nd Edition 1950, pp. 477-478.

Primary'Examiner-James W. Lawrence Assistant Examiner--Wm. H. Punter 57ABSTRACT A spark plug for intemal combustion engines wherein heat rangeiscontrolled by body configuration andthe dissipation of heat through anextended nose portion of the body that extends beyond the reach toprotectively enclose an extended insulator and center electrode, andthat is exposed within the combustion chamber with the spark gappositioned at the eye of combustion and/or at an optimum ignition point.The heat range of the spark plugis efficiently controlled by means ofthe exposure and the fineness ratio of the extended nose portion of thespark plug body and heat transferred therefrom through threadedengagement that'is, of assured tightness adjacent the combustionchamber. A

20 6111.11,, 11 Drawing Figures BACKGROUND AND FIELD OF INVENTIONEfforts to provide clean running internal combustion engines, andparticularly those using the Otto cycle, are met with problems relatedtoand including combustion chamber design, valves and porting, andignition. It is the latter which is most critical and usually acceptedas being in a constant stateof deterioration, due to normal operationandunpredictible' variations in engine use.

Heretofore, spark plugs have been selected for their heat dissipatingability, with the expectation that they will burn clean withoutfoulin'g..That is, the heat range" is the controlling factor ofvirtually all spark plugs, and optimum engine operation is practicallyimpossible to obtain with any one spark plug configuration. Althoughresortis sometimes made to-increased electrical intensity and to sparkplugs of radical design,

those persons skilled in the art have relied exclusively upon thecoil-breaker system andconventional spark plugs wherein the ceramicinsulator is controlling in the determination of heat range. The mostcommon spark plug has a center'electrode insulated from the spark plugbody, and has an overly-' ing grounded electrode. There are surfaceconductor spark plug designs, and it is the so-called "surface gap sparkplug which has concentric'electrodes separated by an insulator. In allexcept the last mentioned surface heat. It is apparent that deepness ofthe spark gap and its projection into the cylinder is to be desired, butthis advantage has been greatly restricted by the adversitiesencountered in dissipating heat through the ceramic insulator. Inpractice, over extension of the core nose in conventional spark plugsresults in overheating and rapid deterioration thereof. An object ofthis invention is to provide for protectionof the electrodes so thatthey can be projected to an optimum position deep within the cylinderand preferably at the eye" of the explosive charge or at the optimumignition point within the combustion chamber. With the presentinvention, it is to be understood that reach remainsas it is in theprior art concerned with the length of the threaded portion of the body,while 'extension" herein refers to the projectionof the spark plugstructure into gap spark plugs, thesaid heat rangef properties are ofimportance toproper engine operation, while in the latter it isdefinitelynot. Another factor to consider is that surface gap sparkplugs are recognized as useable only with the special high-voltageignition systems .and only in specified engines, and they are not usedinterchangeably'with regular type spark plugs. Thus, the state of theart recognizes the affects of heat range and therequirements andinabilities of the wide variety of spark plug designs. And, despite thecareful selection of a conventional spark plug, optimum ignition andflamelator cores that project beyond the threads, but only as aconvenience to project to a satisfactory ignition point at or near thehead and not for the purpose of heat range control. In other'words, theprior art places the spark gap'near'the cylinder head wall'and utilizesthe insulator design and/or configuration to control heat, and it isnoteworthy that a ceramic insulator is a poor conductor of heat.

Same high performance, and racing" spark plugs are made with exposedspark gaps projected somewhat into the cylinders, but'neverthelesslutilizing exposed ceramic insulators to control heat range, And eventhough the threaded bodies are sometimes extended to a slight degree,these bodies are not relied upon to control heat through the threadedconnection into the the combustion chamber of the cylinder.

l-Ieat conduction through a threaded joint is adversely affected .byloose threads while it is enhanced by tight threads. It has beenobserved that the ordinary inner threads adjacent the combustion chamberacquire carbon deposits therebetween and which adversely affects heattransfer; while the outer threads remain clean and tight and whichenhances heat transfer. Since it is-a primary object of this inventionto control heat range with the metallic body of the spark plug, it isalso an object to provide tight threaded engagement at the innermostthreads for increased effect in transferrin'g heat away from the sparkplug body. With the present invention, the leading thread convolutionsare tight and preferably by means of a pitch gain thread localizingtightness around the body adjacent the combustion chamber.

Heretofore, the spark plug electrodes have been located at orclose tothe surface of the [head structure and which requires a richer mixturefor ignition and proper flame propagation as. compared with therequirements of electrodes extended deeply into the combustion chamber.This is, extended electrodes'are known to be beneficial but heretoforesubject to damaging effects due to the inability of dissipating heatthrough the ceramic insulator. It is an object, therefore, to providefor heat controlled electrode extension and for the optimum placementthereof within the combustion chamber, and wherein the spark plug bodyis the instrument for dissipating heat. With the present invention, themetal of the body is selected and configured for efficient and directheat transfer into the head structureof the engine.

Performance is of prime importance and it has been discovered that thespark plug of the present invention made in the variety of knownelectrode forms are most SUMMARY or INVENTION The spark plug hereindisclosed involves, generally, the usual features which include a bodyor shell A and an insulator B with seals S1 and S2 therebetween. The

usual'center electrode C extends through the insulator with a seal S3therebetween, and the ground electrode D is carried by the body tooppose the electrode C. In accordance with this invention an extendednose E is provided to project from the threaded reach portion of thebody A to expose the opposed electrodes deep within the combustionchamber, as shown. It is to be observed that the nose E is anon-threaded structural portion'of the body that projects from thethreaded reach portion thereof, regardless of the'elongation of saidreach portion; and in no case need the thread of said reach portionbecome exposed in the combustion chamber.

DRAWINGS The various objects and features of this invention will befully understood from the following detailed description of the typicalpreferred forms and applications thereof, throughout which descriptionreference is made'to the accompanying drawings, in which:

FIG. 1 is a sectional view through the head portion of an engine showingthe installation of this spark plug.-

FIG. 2 is an enlarged vertical section of the spark plug shown inFIG. 1. FIG. 3 is a view similar to FIG. 2 showing the preferredembodiment. FIGS. 4 and 5 are end views of the spark plugs as takenbylines 4-4 and 55 on FIGS. 2 and 3, respectively. FIG. 6 is a fragmentarysection showing a third form of invention. FIG. 7 is a fragmentarysection of a fourth form of invention. FIG. 8 is a fragmentary sectionof a fifth form of invention. FIG. 9 is an end view taken asindicated byline 99 on FIG. 8. FIGS. 10 and 11 are enlarged fragmentary sectionalviews of the spark plugs of FIGS. 3 and 2 respectively, showing thepitch gain threading for tightness.

PREFERRED EMBODIMENT Referring now to the drawings, a typical combustionchamber is illustrated and which involves the cylinder 10, head 11 andpiston 12 of an engine. A refined configuration is shown wherein boththe head and piston are hemispherical, and since they cooperate inopposition to each other, the chamber formed thereby is more or lessspherical at maximum compression. This is but one engine configurationand is representative of the featuresv involved in creating the .eye'ofthe combustible charge and/or in establishing an optimum ignition point,it being understood that the theoretical center or eye is notnecessarily the optimum point for ignition. And, in accordance with thisinvention the extended nose E projects to what I term the eye ofcombustion and/or optimum ignition point, the geometric center fromwhich flame propagation occurs.

The body or shell A is a metal structure suitably formed of materialhaving the desired heat conductivity commensurate with the design whichcontrols heat range. The body has three .sections including a drivesection 15, a reach section 16, and the extendednose E section. Asshown, the three sections are integrally formed in the manner common tospark plug design; the drive section'being cylindrical with a polygonalhead 17 adapted to be turned by a wrench; the reach section 16 being ofreduced diameter and externally threaded at 18 to be threadedly engagedin the head as hereinafter described; and the extended nose E sectionbeing projected from the aforementioned reach section 16 andcharacteristically devoid of the said threads at 18. An upwardlydisposed shoulder 27 defines the diameter reduction between the sectionsand 16, and

in the case illustrated the body or shell A is characterized by anenlarged upper diameter body 19 and by a reduced lower diameter bore 20,said bores 19 and 20 opening at the upper and lower extremities of thebody respectively.

The insulator B is a ceramic element usually formed of aluminum-oxidehaving a cylindrical body 21 engaged in the bore 19 and with upwardlyand downwardly projecting stem and nose portions 22 and 23. The body 21presents upwardly and downwardly faced shoulders 24 and 25 where theseals S1 and S2 capture and position the elements A and B relative toeach other. The seal S1 is a sillment of powered material such asaluminum-silicate or sillimanite (fibrolite) that is compacted beneathan intumed flange 26 of the body A; while the seal S2 is a gasket ringsupported upon shoulder 27 to engage the insulator body. The sternportion 22 projects from the bore 19 and well above the body A, whilethe nose portion 23 projects through the reach section 16 and into theextended nose E. An electrode bore 30 extends through the insulator B.

The center electrode C is a rod of electrically conductive material thatextends through the bore 30 for exposure at the tip of the nose portion23 and at the terminal end of stem portion 22. The bore 30 iscounterbored at 31 so as to receive and provide a shoulder to locate anenlargement positioning the said electrode.

The reach section 16 is coextensively threaded and surrounds both theinsulator nose portion 23 and electrode C extending therethrough, and itcarries the extended nose E which continues to surround both theinsulator nose portion 23 and electrode C extending therethrough.

In accordance with the present invention, I'provide the extended nose Efor optimum placement of the electrodes C andD and for heat rangecontrol. The said,

nose is comprised of a tubular continuation of the spark plug body A andcharacterized by a right cylinder wall of predetermined fineness ratio.As shown, the bore 20 establishes the inner. diameter wall thereof whilethe outer diameter wall 35 is smaller than the inner diameter of thethreads at 18. In practice, the nominal extension (longitudinalcontinuation) of the nose E can be equal to and in some instancesgreater than the longitudinal extent of the reach section 16, therebyplacing the spark gap between the electrodes at the eye" or optimumpoint of ignition as circumstances require. As shown in FIG. 5, thegrounded electrode D is a finger 36 that projects outwardly and radiallyinward from the terminal end of nose E, to overlie the center electrodeC with the spark gap exposure substantially as shown and as may berequired. As shown in FIG. 4, the grounded electrode D is the circularterminal end portion of the nose E per se, concentrically surroundingthe center electrode C with the terminal end of the insulator nose 23recessed slightly and in a normal plane extending radially therebetween.

The cylindrical wall of the extended nose E protectively e'ncases theinsulator nose 23 which electrically shields the'outer electrode Cexcept for the small nor- -mally exposed tip portion thereof. Precisepositioning position the spark gap as particular circumstances re quire.v

In accordance withthis invention, heat range is controlled by determinedvariation in thickness of the exposed metal of the tubular wall of noseE, bythe configuration thereof, by theproperties of the metals employedtherein, and by the location of the-contact area of the threads at 18adjacent the combustion chamber. In carrying out this invention, it hasbeen found to be most practical to construct ceramic insulators Bof agiven size, conventionally sealed at S2 as shown in a body-shell A ofagiven nominally thick wall in the extended nose E; The heat range isthen controlled by in- .creasing or reducing the wallthickness of thetubular nose E, so that the electrodes and immediate spark plugstructure operate at .the desired temperature in the engine for which itis intended.

Referring now to FIGS. and 11, and the aforesaid pitch gain thread, 'thelowermost thread convolutions at 18 and preferably two or three turnsthereof next adjacent to the extended nose E are altered so as totightly engage into, the threaded bore .in the engine head 11. It iscontemplated that the engine head threads remain uniform and thatonlythe spark plug be modified in this respect, although either one orboth threads can be so modified. Further, there are various ways inwhich to provide tight threadswhere specified it being preferred asshown in FIG. 11 that a localized gain in pitch be provided in thelowermost thread convolutions, 'or as shown in FIG. 10 that a uniformgain pitch be provided through the entire reach length. Thus, anunusually efficient and increased thread contact is provided and and useof gaskets and by controlling the thickness and- I which assures adirect path for conducting heat into the head from the immediatelydependent extended nose E of the spark plug. I

Referring to the embodiment of FIG. 6, retension of heat at the sparkgap is provided for with a restriction of heatflow into and through thethreaded reach portion. As shown, the lowermost end portionof theextended nose electrode is reduced at its outer diameter by means of anencompassing groove 50, with an upwardly flared outer diameter wall 51extending therefrom to the threaded reach portion, and with-a down--wardly flared outer diameter wall 52 extending therefrom to a terminalend enlargement 53. This configuration provides for heat retension atthe electrode and re stricts the flow of heat as determined by the depthof the groove. Reference is made to FIG. 3wherein heat flow is inducedinto the threaded reach section by means of an upwardly and inwardlytapered inner diameter wall leading to the reach section, and acontinuing upwardly and outwardly tapered inner diameter wall leadingtherefrom to the drive section.

Referring to the embodiment of FIG. 7, the control of flame propagationis in the shape of an electrode which is concaved at 54 for focusing thepropagation of the flame front to a convergence. As shown, the uppermostend portion of the extended nose electrode is reduced in diameter'whereit joins to the threads 18 of Referring now to the embodiment of FIGS. 8and 9, the control of flame propagation is in an electrode in which theflame front propagates from a ribbed surface preferably normal to theplug axis, as shown. In the broad sense, ribs 55 are extended'as may berequired to receive and direct the flow, the swirl, of gases. Therefore,and dependent 'upon combustion chamber design and characteristics, theribs 55 are shaped to receive swirling gases and to advantageouslygovern the angular momentum thereof; and, for example, and as shown, byan involute curvature thereof which directs the gases into the gap(surface gap) area of the extended nose plug. FIG. 9 illustrates atypical rib configuration which has gas directing capability and heatcol- -lecting capability as well, and all of which is correlated 'to theheat dissipating capability of the extended nose E as hereinabovedescribed.

From the foregoing it will be observed that the spark gap can'be placedat the optimum position within the combustion chamber and provided withthe desired heat range by selecting the required nose extension /orfineness ratio and/or configuration of the said extended nose. Theextended nose of this spark plug gives up heat to the fuel droplets thatimpinge thereupon, converting them into vapor and further enhancing thecombustibility of the fuel mixture. The ceramic insulator is no longerthe determining factor for heat range, but is merely incidental inthat'the extended nose of the body is configured so as to runsufficiently hot so as to be self-cleaning and so as to convert theimpinging fuel droplets into a true vapor. Thus, the ceramicinsulatorcan be reduced in diameter so as to permit increased wall thickness inthe extendednose which has for its primary purpose the transfer-of heatinto the head structure of the engine to be dissipated thereby. Byproviding a spark plug structure suitable for theextension of theelectrodes to the eye or optimum ignition point, flame propagationisbrought into corresponding control for providing clean running internalcombustion engines.

Having described only a typical preferred form and I application of myinvention, I do'not wish to be limited the reach portion, and flares downwardly to a terminal end enlargement 53'. It will be observed that theconvex electrode of FIGS. 2 and 6 control a flame propagation that isdivergent, in comparison; and it is to be understood that this sparkplug can be constructed with any variation of convexity to concavityranging between the two illustration-s' substantially as shown.

or restricted to the specific details herein set forth, but wish toreserve to myself any modiflcations or variations that may appear tothose skilled in the art:

I claim:

1. A heat range controlling spark plug for extending the spark gap to anoptimum ignition point away from the combustion chamber wall, andincluding; an integral heat conductive body comprised of an outer drivesection and an intermediatereach section and an inner nose section,there being a bore extending through said body sections, aninsulatorcomprised of a dielectric engageably carried in the bore with astem portion projecting from the drive section of the body and withanose portion projecting through the reach and nose sections of thebody, there being a boreextending the terminal end of the noseportion-of the insulator, the reach portion of the body having heatconductive threads for mounting engagement through a combustion chamberwall, and the nose section of the heat 4 conductive body being ofcylindricalftube form extended protectively over the insulator noseportion and with a predetermined fineness to length ratio determinativeof heat transfer therethrough and dissipation thereof into theintermediate reach section and projecting into said combustion chamberwith an electrode at its innermost terminal end opposed to the saidother innermost end of the first mentioned electrode.

2. The heat range and extended gap spark plug as set forth in claim 1wherein the cylindrical tube form of the nose section has a wall oftapered heat controlling configuration.

3. The heat range and extended gap spark plug as set forth in claim 1wherein the nose section has a convexly shaped terminal end heatcontrolling configuration.-

4. The heat range and extended gap spark plug as set forth in claim 1wherein the nose section has a concavely shaped terminal endflamepropagation configuration.

5. The heat range and extended gap spark plug as set forth in claim 1wherein the diametral terminal end of the nose section is ribbed.

6. The heat range and extended gap spark plug as set forth in claim 1wherein the nose section has radially disposed involutely curved ribsprojecting from its terminal end.

7. The heat range and extended gap spark plug as set forth in claim 1wherein the electrode at the innermost end of the inner nose section iscomprised of a finger extending radially inward to oppose the said firstmentioned electrode.

8. The heat range and extended gap spark plug as set forth in claim 1wherein the electrode at the innermost end of the inner nose sectioniscomprised of a bore therethrough spaced concentrically around the saidfirst mentioned electrode forming an air gap therebetween.

9. The heat range and extended gap spark plug as set forth in claim 1wherein the insulator is substantially longitudinally coextensive withthe inner nose section of the heat conductive body.

10. The heat range and extended gap spark plug as set forth in claim 1wherein the insulator is substantially longitudinally coextensivewiththe inner nose section of the heat conductive body, and wherein theelectrode at theinnermost end of the inner nose section is comprised ofa finger extending radially inward to oppose the said first mentionedelectrode.

11. The heat range and extended gap spark plug as set forth in claim 1wherein the insulator is substantially longitudinally coextensive. withthe inner nose section of the heat conductive body, and wherein theelectrode at the innermost end of the inner nose section is comprised ofthe bore therethrough spaced concentrically around the said firstmentioned electrode.

12. A controlled heat range spark plug for extending the spark gap to anoptimum ignition point away from the combustion chamber wall, andincluding; an integral heat conductive body comprised of an outerdrivesection and in intermediate reach section and an inner nose section,there being a bore extending through said body sections, an insulatorcomprised of a dielectric engageably carried in the bore with a stemportion projecting from the drive section of the body and with a noseportion projecting through the reach and nose sections of the body,there being a bore extending through said insulator body, and anelectrode extending through the last mentioned bore and with anoutermost terminal end exposed at the stem portion of the insulator andwith another innermost end exposed at the terminal end of the noseportion of the insulator, the reach portion of the body having heatconductive threads for mounting engagement through a combustion chamberwall, and the nose sections of the heat conductive body being ofcylindrical tube form having dimensionally predetermined inner and outerdiameter walls commensurate with the fineness to length ratiodeterminative of heat transfer therethrough and dissipation thereof intothe intermediate reach section and extended protectively over theinsulator nose portion and projecting into said combustion chamber withan electrode at its innermost terminal end opposed to the said otherinnermost end of the first mentioned electrode.

13. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the said nose section of the heat conductive body isgrooved intermediate its inner and outer extremities for restriction of14. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the said nose section of the heat conductive body isgrooved spaced from its innermost end with a terminal end portion of thenose section remaining to retain heat and for restriction of heat flowinto the said intermediate reach section.

15. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the convolutions of the heat conductive threads ofthe reach section and adjacent to the extended nose section of the heatconductive body are more tightly threaded through the combustion chamberwall than the remaining convolutions thereof.

16. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the convolutions of the heat conductive threads ofthe reach section and adjacent to the extended nose section of the heatconductive body are of greater ptich than the remaining convolutionsthereof.

17. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the convolutions of the heat conductive threads ofthe reach section and adjacent to the extended nose section of the heatconductive body are of different pitch than the complementary threadsthrough the combustion chamber wall.

18. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the nose section of cylindrical tube form is ofenlarged configuration at its terminal end.

19. The controlled heat range and extended gap sparkplug as set forth inclaim 12 wherein the nose section of cylindrical tube form is ofenlarged convex configuration at its terminal end.

20. The controlled heat range and extended gap spark plug as set forthin claim 12 wherein the nose section of cylindrical tube form is ofenlarged concave configuration at its terminal end.

1. A heat range controlling spark plug for extending the spark gap to an optimum ignition point away from the combustion chamber wall, and including; an integral heat conductive body comprised of an outer drive section and an intermediate reach section and an inner nose section, there being a bore extending through said body sections, an insulator comprised of a dielectric engageably carried in the bore with a stem portion projecting from the drive section of the body and with a nose portion projecting through the reach and nose sections of the body, there being a bore extending through said insulator body, and an electrode extending through the last mentioned bore and with an outermost terminal end exposed at the stem portion of the insulator and with another innermost end exposed at the terminal end of the nose portion of the insulator, the reach portion of the body having heat conductive threads for mounting engagement through a combustion chamber wall, and the nose section of the heat conductive body being of cylindrical tube form extended protectively over the insulator nose portion and with a predetermined fineness to length ratio determinative of heat transfer therethrough and dissipation thereof into the intermediate reach section and projecting into said combustion chamber with an electrode at its innermost terminal end opposed to the said other innermost end of the first mentioned electrode.
 2. The heat range and extended gap spark plug as set forth in claim 1 wherein the cylindrical tube form of the nose section has a wall of tapered heat controlling configuration.
 3. The heat range and extended gap spark plug as set forth in claim 1 wherein the nose section has a convexly shaped terminal end heat controlling configuration.
 4. The heat range and extended gap spark plug as set forth in claim 1 wherein the nose section has a concavely shaped terminal end flame propagation configuration.
 5. The heat range and extended gap spark plug as set forth in claim 1 wherein the diametral terminal end of the nose section is ribbed.
 6. The heat range and extended gap spark plug as set forth in claim 1 wherein the nose section has radially disposed involutely curved ribs projecting from its terminal end.
 7. The heat range and extended gap spark plug as set forth in claim 1 wherein the electrode at the innermost end of the iNner nose section is comprised of a finger extending radially inward to oppose the said first mentioned electrode.
 8. The heat range and extended gap spark plug as set forth in claim 1 wherein the electrode at the innermost end of the inner nose section is comprised of a bore therethrough spaced concentrically around the said first mentioned electrode forming an air gap therebetween.
 9. The heat range and extended gap spark plug as set forth in claim 1 wherein the insulator is substantially longitudinally coextensive with the inner nose section of the heat conductive body.
 10. The heat range and extended gap spark plug as set forth in claim 1 wherein the insulator is substantially longitudinally coextensive with the inner nose section of the heat conductive body, and wherein the electrode at the innermost end of the inner nose section is comprised of a finger extending radially inward to oppose the said first mentioned electrode.
 11. The heat range and extended gap spark plug as set forth in claim 1 wherein the insulator is substantially longitudinally coextensive with the inner nose section of the heat conductive body, and wherein the electrode at the innermost end of the inner nose section is comprised of the bore therethrough spaced concentrically around the said first mentioned electrode.
 12. A controlled heat range spark plug for extending the spark gap to an optimum ignition point away from the combustion chamber wall, and including; an integral heat conductive body comprised of an outer drive section and in intermediate reach section and an inner nose section, there being a bore extending through said body sections, an insulator comprised of a dielectric engageably carried in the bore with a stem portion projecting from the drive section of the body and with a nose portion projecting through the reach and nose sections of the body, there being a bore extending through said insulator body, and an electrode extending through the last mentioned bore and with an outermost terminal end exposed at the stem portion of the insulator and with another innermost end exposed at the terminal end of the nose portion of the insulator, the reach portion of the body having heat conductive threads for mounting engagement through a combustion chamber wall, and the nose sections of the heat conductive body being of cylindrical tube form having dimensionally predetermined inner and outer diameter walls commensurate with the fineness to length ratio determinative of heat transfer therethrough and dissipation thereof into the intermediate reach section and extended protectively over the insulator nose portion and projecting into said combustion chamber with an electrode at its innermost terminal end opposed to the said other innermost end of the first mentioned electrode.
 13. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the said nose section of the heat conductive body is grooved intermediate its inner and outer extremities for restriction of heat flow.
 14. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the said nose section of the heat conductive body is grooved spaced from its innermost end with a terminal end portion of the nose section remaining to retain heat and for restriction of heat flow into the said intermediate reach section.
 15. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the convolutions of the heat conductive threads of the reach section and adjacent to the extended nose section of the heat conductive body are more tightly threaded through the combustion chamber wall than the remaining convolutions thereof.
 16. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the convolutions of the heat conductive threads of the reach section and adjacent to the extended nose section of the heat conductive body are of greater ptich than the remaining convolutions thereof.
 17. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the convolutions of the heat conductive threads of the reach section and adjacent to the extended nose section of the heat conductive body are of different pitch than the complementary threads through the combustion chamber wall.
 18. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the nose section of cylindrical tube form is of enlarged configuration at its terminal end.
 19. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the nose section of cylindrical tube form is of enlarged convex configuration at its terminal end.
 20. The controlled heat range and extended gap spark plug as set forth in claim 12 wherein the nose section of cylindrical tube form is of enlarged concave configuration at its terminal end. 